Field of the Invention
The invention relates to a device for transferring sheets in a sheet-processing machine, in particular a sheet-fed printing machine, having a cylinder with at least one gripper device for the sheets, and with a control device for opening and closing the gripper device.
In transfer devices of the type referred to herein, which include at least one cylinder having a gripper device by the periphery of which a sheet, for example, a paper sheet, is transferred, the opening and closing of the gripper device holding the sheet at the leading edge thereof is performed based upon the rotary angle position of the cylinder. Provided for this purpose is a control device, which includes at least one control cam completely enclosing a bearing journal of the cylinder and having an outer contour followed by a follower element coupled to the gripper device. In this case, the follower element is supported continuously on the closed curved path of the control cam. The control cam is disposed in a fixed position with respect to the rotating cylinder, for example, fastened to a side wall of the machine, and is formed with a through opening through which the bearing journal extends.
The assembly or mounting of the control cam is normally readily possible before the cylinder is inserted, in that it is pushed onto the bearing journal. The adjustment for setting the gripper opening/closing times is achieved by rotating the control cam with respect to the side wall which is in a fixed position, so that format adjustment of the sheets is possible. It has been shown that the control cam, for example, as a result of failure of the follower element, for example, because of a lack of lubrication or due to a fault in the material, can be damaged, which makes the replacement thereof necessary. One possibility for sliding the control cam down off the bearing journal in the axial direction requires the removal of the side wall, which is possible only with a very great amount of effort. One further possibility is to break the control cam, which again is made more difficult by the poor accessibility thereof. Use has therefore already been made, even during initial assembly or mounting, of divided control cams, which are detachably connected to one another. A disadvantage here is that the fabrication, assembly or mounting and adjustment of the multipartite control cam is very complicated and therefore costly.
The published German Patent Document GM 79 27 115 U1 reveals a transfer device which has a multipartite control cam. As viewed in cross section, the control cam has a U-shaped basic body, which can be pushed over the bearing journals in radial direction with respect to the axis of rotation of the cylinder. In order to implement a closed cam path, the open region of the basic body is then supplemented by a short cam segment, which is pinned and screwed to the basic body. A disadvantage thereof is that the production and assembly/disassembly or mounting/removal of the control cam is very complicated.
In addition, U.S. Pat. No. 4,535,691 discloses a transfer device that is installed in sheet-fed printing machines, which are capable of being operated selectively or optionally in recto or first-form printing and in recto/verso or first-form and perfector printing. For this purpose, the opening range of the gripper device, i.e., the rotary angle position of the cylinder wherein the gripper device is opened, up to the rotary angle position of the cylinder at which it is closed again in order to release the sheet, is constructed so as to be adjustable, while the closing range of the gripper device, in order to accept the sheet from a preceding printing unit, for example, is always the same. For this purpose, a control device is used which has two control cams, a first, fixed-position control cam for performing the complete guidance of the follower element in the recto printing operation, while a second control cam, which can be adjusted in the peripheral direction with respect to the first control cam, is located in a nonfunctioning waiting position during the recto printing operation. In recto/verso of first-form and perfector printing, the second control cam is adjusted in order to shift the opening time of the gripper device. In this case, the first and the second control cams then provide one movement section, respectively. A disadvantage of this construction is that the first control cam used for recto printing must be of closed construction, the assembly and disassembly or mounting and removal of the control cam being made more difficult in the case of a unipartite configuration, and the manufacture of the control cam being costly in the case of a multipartite configuration thereof.
It is therefore an object of the invention to provide a transfer device of the type mentioned at the introduction hereto wherein, even with the cylinder already assembled or mounted, the at least one control cam can be assembled and disassembled or mounted and removed simply and thus, preferably, can be produced simply and therefore cost-effectively.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for transferring sheets in a sheet-processing machine, comprising a cylinder having at least one gripper device for the sheets, and a control device for opening and closing the gripper device, the control device having a first control cam for recto printing and a second control cam for recto/verso printing, at least one follower element for following the first and second control cams, each of the first and second control cams being formed with a through opening for accommodating a bearing element and, respectively, a cutout formed in the periphery of the first and second control cams and extending as far as the through opening for fitting the first and second control cams to and removing them from the bearing element radially, the first and second control cams, respectively, being of unipartite construction and, in peripheral direction, being aligned with one another so as to provide an at least approximately closed contour path for the at least one follower element.
In accordance with another feature of the invention, at least one of the first and second control cams is rotatable with respect to the other thereof for adjusting opening and closing times of the gripper device.
In accordance with a further feature of the invention, the cutout formed in at least one of the first and the second control cams has a width which is at least as large as the outer diameter of the bearing element, and is at maximum only sufficiently large for a wall defining said through opening to be interrupted by the cutout over a peripheral range of less than 180xc2x0.
In accordance with an added feature of the invention, the gripper device is actuatable by the follower element, and the cutout in the first control for recto printing is disposed in a peripheral region wherein the gripper device actuatable by the follower element is inactive during recto printing.
In accordance with an additional feature of the invention, the first and second control cams are formed and aligned with one another in a manner that guide paths thereof for the follower element, in recto printing and recto/verso printing, overlap in at least one peripheral region of the first and second control cams.
In accordance with yet another feature of the invention, the transfer device includes an actuating drive for aligning the first and the second control cams with one another in peripheral direction.
In accordance with yet a further feature of the invention, the transfer device includes structure provided for manually performing the alignment of the first and the second control cams with one another in peripheral direction.
In accordance with yet an added feature of the invention, the first control cam is fixed to a frame fixed in position, and the second control cam is adjustable in peripheral direction with respect to the first control cam.
In accordance with yet an additional feature of the invention, the second control cam has a toothing system, and the actuating drive has at least one gearwheel to which a torque is applicable and which is one of being engaged with and being engageable with the toothing system.
In accordance with still another feature of the invention, the first and the second control cams, respectively, have at least two outer peripheral sections with different radii, a transition from one of the outer peripheral sections to another of the outer peripheral sections disposed adjacent thereto being at least approximately stepless.
In accordance with still a further feature of the invention, the outer peripheral sections are circular path sections.
In accordance with still an added feature of the invention, the transfer device includes at least one stop for defining at least one of a maximum opening position and a closing position of the gripper device.
In accordance with still an additional feature of the invention, the cylinder is a storage cylinder.
In accordance with another feature of the invention, the cylinder is a storage impression cylinder.
In accordance with a further feature of the invention, the transfer device forms part of a sheet turning or reversing device which, as viewed in the sheet travel direction, has a transfer/turning or reversing drum disposed downline from the cylinder.
In accordance with an added feature of the invention, the follower element is formed by at least two cam rollers disposed adjacent one another, a first one of the cam rollers following the first control cam, and a second one of the cam rollers following the second control cam.
In accordance with an additional feature of the invention, the follower element is formed by a wide cam roller for following both the first and the second control cams.
In accordance with yet another feature of the invention, the cam roller is of double convex form and, in the peripheral regions, the cam roller rests on contour paths of the first and the second control cams.
In accordance with a concomitant feature of the invention, the first and the second control cams, respectively, in the peripheral direction, upline and downline from the cutout thereof, have a lowered portion with respect to the outer peripheral surface of the respective other control cam.
Thus, in order to attain the objective of the invention, a device for transferring sheets in a sheet-processing machine is proposed which has a cylinder with at least one gripper device for the sheets, the opening and closing and/or the times for opening and closing the gripper device in relation to the rotary angle position of the cylinder being performed or being adjustable by a control device. The control device has a first control cam for recto printing and a second control cam for recto/verso printing, both cams being followed by at least one follower element, for example a cam roller. The control cams, respectively, are formed with a through opening for accommodating a bearing element, in particular a bearing journal, of the cylinder and, in each case, a cutout provided in the periphery of the control cams and extending as far as the through opening to permit the control cam to be fitted to and removed from the bearing element radially. Each control cam, viewed by itself, respectively, therefore has no closed outer contour, i.e., a contour track, which can be followed by the follower element. The width of the cutout is at least as great as or greater than the outer diameter of the bearing element. The transfer device is distinguished by the fact that the first and second control cams are formed in one piece and, in the peripheral direction, are aligned with one another so that there results a preferably completely closed, but at least approximately closed, contour path for the follower element. Because of the single part or integral configuration, the control cams can be produced cost-effectively. It is also advantageous that the mounting and removal or assembly and disassembly are also readily possible even if the cylinder has already been installed in the machine.
The contour path which can be followed is composed of the guide paths interrupted by the respective cutout in the control cams, i.e., outer peripheral area sections. The control cams are preferably aligned with one another in recto printing and in recto/verso printing so that the cutouts in the control cams do not overlap one another, which would result in the production of a gap in the contour path, which would then be swept over by the follower element during each revolution of the cylinder. The rotary alignment of the control cams in relation to one another is preferably selected so that the contour path is always completely closed, i.e., both in recto printing and in recto/verso printing, and for any format of the sheets to be transferred.
In a preferred embodiment of the transfer device, in order to adjust the opening and closing times of the gripper device in relation to a specific rotary angle position of the cylinder, at least one of the control cams can be rotated with respect to the other control cam. In an advantageous alternative construction, both control cams are centered on the bearing element, so that here rotation of the control cams is carried out about the axis of rotation of the cylinder. The bearing element has a circular cross section, at least in the region of the through openings in the control cams, so that stepless adjustment of the control cams with respect to one another is readily possible.
In an advantageous exemplary embodiment of the transfer device, provision is made for the maximum width of the cutout in the first control cam and/or in the second control cam to be only so great that the wall of the through opening provided in the control cam is interrupted by the cutout over a peripheral range which is less than 180xc2x0. The cutout is therefore, firstly, so large that the control cam can be pushed radially, in the direction as referred to the axis of rotation of the cylinder, onto the bearing element, but the dimensions thereof are selected so as to be so small that the peripheral range of the through opening which is available for centering the control cam with respect to the bearing element is still sufficiently large to ensure reliable centering.
Preference is also given to an exemplary embodiment of the transfer device which is distinguished by the fact that the cutout in the first control cam, used for recto printing, is arranged in a peripheral region wherein the gripper device actuated by the follower element does not deliver any printing material during recto printing, preferably being open. In this case, the cutout is located during recto printing at a point at which the gripper device is opened and is therefore inactive; this means that no sheet is held by the gripper device. In the region of this cutout, the pressing force of the follower element on the guide path or paths of the control cam or cams, respectively, is only low. At the point at which the gripper device is open during recto printing, the contour path which is followed by the follower element and which is composed of parts of the respective guide path of the individual control cams, preferably has a lowering region. This may be understood to mean that the gripper device is closed when, based upon the curved course of the contour path, it is at a radially greater distance from the axis of rotation of the cylinder, while it is opened in that region of the contour path which is located closer to the axis of rotation.
According to a development of the invention, provision is made for the first and second control cams to be formed and aligned with one another in the peripheral direction so that the guide paths thereof for the follower element in recto printing and recto/verso printing overlap in at least one peripheral region of the control cams. As a result, it is possible to ensure that the follower element is always supported by at least one of the two cams during a complete revolution of the cylinder. It is also advantageous that further tolerances can be implemented in producing the cutouts in the control cams.
Preference is also given to an exemplary embodiment of the transfer device wherein, in order to align the first and second control cams with one another in the peripheral direction, an actuating drive is provided. As a result, automatic adjustment of the control cams in relation to one another, i.e., setting the opening and closing times of the gripper device, is possible. According to an alternative construction, provision is made for the alignment to be carried out manually, which means that a simpler construction of the transfer device can be implemented. Of course, it is also possible for the actuating drive to offer an option for manual alignment as well.
Furthermore, preference is given to an exemplary embodiment of the transfer device which is distinguished by the fact that the first control cam is fixed to a frame which is in a fixed position, for example, fixed to a side wall of the machine, and the second control cam can be adjusted in the peripheral direction with respect to the first control cam. In this embodiment, therefore, only the second control cam is moved in the peripheral direction in relation to the first control cam in order to adjust the opening and closing times of the gripper device, as referred to the rotary angle position of the cylinder.
In a further embodiment, the second control cam has a toothing system which runs concentrically with respect to the axis of rotation and with which a gearwheel which belongs to the actuating drive and to which a torque can be applied is or can be engaged. Thereby, very exact adjustment of the rotary angle position of the second control cam with respect to the first control cam is possible.
In an advantageous exemplary embodiment of the transfer device, provision is made for each of the first and second control cams, upline and downline of the cutout thereof in the peripheral direction, respectively, to have a lowered portion which is covered by the respective other control cams closing the cutout, which means that the transition from one outer peripheral section of the first control cam to an outer peripheral section of the second control cam, arranged adjacent thereto, is at least approximately stepless. This makes it possible to ensure that the contour path, which is composed of the guide paths of the control cams and is followed by the follower element, has a curved course without edges, so that the actions of opening and closing the gripper device are not carried out abruptly but gradually. In addition, it is possible to ensure that the transition of the follower element from the guide path of one control cam to the guide path of the other control cam also takes place gradually, so that differences in diameter between the control cams resulting during manufacture or assembly are compensated for.
According to a development of the transfer device, at least one stop is provided in order to define the maximum opening position and/or closing position of the gripper device. This makes it possible to ensure that, if there is a gap in the contour path, for example, as a result of an overlapping of the cutouts in the control cams, the opening or closing of the gripper device beyond the normal functional position thereof is avoided. Damage to the gripper device, which, for example, is pivotable about an axis and has a gripper shaft, by other parts of the transfer device can therefore be ruled out.
In an advantageous exemplary embodiment, the cylinder of the transfer device according to the invention is formed by a buffer or storage cylinder, in particular by a storage impression cylinder, at which, during the transfer of the sheet, the sheet resting on the cylinder is printed or varnished by a peripheral region of the cylinder.
In a preferred embodiment, the transfer device is part of a apparatus for turning or reversing the sheets, which, as viewed in the sheet travel direction, has a transfer/turning or reversing drum arranged downline of the cylinder. While the sheet-processing machine is being used for recto printing, the transfer/turning or reversing drum arranged downline of the cylinder serves only for the onward transport of the sheet, which is not turned or reversed. If the machine is set for the recto/verso printing mode, the sheet transferred to the drum by the cylinder is turned or reversed with the aid of the transfer/turning or reversing drum, i.e., the previous trailing edge of said sheet is gripped by a holding device on the turning or reversing drum and then becomes the leading edge, while the previous leading edge of the sheet becomes the trailing edge. It is evident that the transfer device according to the invention can be used universally, i.e., both in machines which are used only for recto or first-form printing or only for verso or perfector printing or for both recto/verso printing or first-form and perfector printing.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for transferring sheets, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: